Buggy code:
public class JavaCorePreferenceInitializer extends AbstractPreferenceInitializer { public void initializeDefaultPreferences ( ) { HashSet optionNames = JavaModelManager . getJavaModelManager ( ) . optionNames ; Map defaultOptionsMap = new CompilerOptions ( ) . getMap ( ) ; defaultOptionsMap . put ( JavaCore . COMPILER_LOCAL_VARIABLE_ATTR , JavaCore . GENERATE ) ; defaultOptionsMap . put ( JavaCore . COMPILER_CODEGEN_UNUSED_LOCAL , JavaCore . PRESERVE ) ; defaultOptionsMap . put ( JavaCore . COMPILER_TASK_TAGS , JavaCore . DEFAULT_TASK_TAGS ) ; defaultOptionsMap . put ( JavaCore . COMPILER_TASK_PRIORITIES , JavaCore . DEFAULT_TASK_PRIORITIES ) ; defaultOptionsMap . put ( JavaCore . COMPILER_TASK_CASE_SENSITIVE , JavaCore . ENABLED ) ; defaultOptionsMap . put ( JavaCore . COMPILER_DOC_COMMENT_SUPPORT , JavaCore . ENABLED ) ; defaultOptionsMap . put ( JavaCore . COMPILER_PB_FORBIDDEN_REFERENCE , JavaCore . ERROR ) ; defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_RESOURCE_COPY_FILTER , "" ) ; defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_INVALID_CLASSPATH , JavaCore . ABORT ) ; defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_DUPLICATE_RESOURCE , JavaCore . WARNING ) ; defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_CLEAN_OUTPUT_FOLDER , JavaCore . CLEAN ) ; <START_BUG> defaultOptionsMap . put ( CORE_JAVA_BUILD_MAKE_OUTPUT_FOLDER_CONSISTENT , JavaCore . IGNORE ) ; <END_BUG> defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_ORDER , JavaCore . IGNORE ) ; defaultOptionsMap . put ( JavaCore . CORE_INCOMPLETE_CLASSPATH , JavaCore . ERROR ) ; defaultOptionsMap . put ( JavaCore . CORE_CIRCULAR_CLASSPATH , JavaCore . ERROR ) ; defaultOptionsMap . put ( JavaCore . CORE_INCOMPATIBLE_JDK_LEVEL , JavaCore . IGNORE ) ; defaultOptionsMap . put ( JavaCore . CORE_ENABLE_CLASSPATH_EXCLUSION_PATTERNS , JavaCore . ENABLED ) ; defaultOptionsMap . put ( JavaCore . CORE_ENABLE_CLASSPATH_MULTIPLE_OUTPUT_LOCATIONS , JavaCore . ENABLED ) ; optionNames . add ( JavaCore . CORE_ENCODING ) ; Map codeFormatterOptionsMap = DefaultCodeFormatterConstants . getEclipseDefaultSettings ( ) ; for ( Iterator iter = codeFormatterOptionsMap . entrySet ( ) . iterator ( ) ; iter . hasNext ( ) ; ) { Map . Entry entry = ( ( Map . Entry ) ( iter . next ( ) ) ) ; String optionName = ( ( String ) ( entry . getKey ( ) ) ) ; defaultOptionsMap . put ( optionName , entry . getValue ( ) ) ; optionNames . add ( optionName ) ; } defaultOptionsMap . put ( JavaCore . CODEASSIST_VISIBILITY_CHECK , JavaCore . DISABLED ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_DEPRECATION_CHECK , JavaCore . DISABLED ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_IMPLICIT_QUALIFICATION , JavaCore . DISABLED ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_FIELD_PREFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_STATIC_FIELD_PREFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_LOCAL_PREFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_ARGUMENT_PREFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_FIELD_SUFFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_STATIC_FIELD_SUFFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_LOCAL_SUFFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_ARGUMENT_SUFFIXES , "" ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_FORBIDDEN_REFERENCE_CHECK , JavaCore . ENABLED ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_DISCOURAGED_REFERENCE_CHECK , JavaCore . DISABLED ) ; defaultOptionsMap . put ( JavaCore . CODEASSIST_CAMEL_CASE_MATCH , JavaCore . ENABLED ) ; defaultOptionsMap . put ( JavaCore . TIMEOUT_FOR_PARAMETER_NAME_FROM_ATTACHED_JAVADOC , "50" ) ; IEclipsePreferences defaultPreferences = ( ( IScopeContext ) ( new DefaultScope ( ) ) ) . getNode ( JavaCore . PLUGIN_ID ) ; for ( Iterator iter = defaultOptionsMap . entrySet ( ) . iterator ( ) ; iter . hasNext ( ) ; ) { Map . Entry entry = ( ( Map . Entry ) ( iter . next ( ) ) ) ; String optionName = ( ( String ) ( entry . getKey ( ) ) ) ; defaultPreferences . put ( optionName , ( ( String ) ( entry . getValue ( ) ) ) ) ; optionNames . add ( optionName ) ; } } }

Fix:
defaultOptionsMap . put ( JavaCore . CORE_JAVA_BUILD_RECREATE_MODIFIED_CLASS_FILES_IN_OUTPUT_FOLDER , JavaCore . IGNORE ) ;